U.S. patent application number 10/977059 was filed with the patent office on 2005-06-23 for transceiver for a base station with smart antenna and a switched beamforming method in downlink.
Invention is credited to Bang, Seung-Chan, Jwa, Hye-Kyung, Kim, Il-Gyu.
Application Number | 20050136980 10/977059 |
Document ID | / |
Family ID | 34680738 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050136980 |
Kind Code |
A1 |
Kim, Il-Gyu ; et
al. |
June 23, 2005 |
Transceiver for a base station with smart antenna and a switched
beamforming method in downlink
Abstract
Disclosed is a transceiver for a base station with a smart
antenna having a plurality of antennas. The transceiver comprises:
a multipath searching unit for searching multipath delay
information for each demodulation channel; a demodulating unit for
forming an adaptive beam for each demodulation channel by using the
multipath delay information for each demodulation channel for
receiving signals and performing demodulation to the received
signals and outputting at least one adaptive beam weight vector; a
controlling unit for selecting at least one downlink beam index for
each channel; and a modulating unit for selecting the downlink
switched beams and forming switching beam for modulating signals of
each channel and outputting the modulated signals in downlink.
Inventors: |
Kim, Il-Gyu; (Seoul, KR)
; Jwa, Hye-Kyung; (Daejeon-city, KR) ; Bang,
Seung-Chan; (Daejeon-city, KR) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN
12400 WILSHIRE BOULEVARD
SEVENTH FLOOR
LOS ANGELES
CA
90025-1030
US
|
Family ID: |
34680738 |
Appl. No.: |
10/977059 |
Filed: |
October 29, 2004 |
Current U.S.
Class: |
455/562.1 ;
455/561; 455/73 |
Current CPC
Class: |
H04B 7/0617 20130101;
H01Q 3/24 20130101; H04B 7/086 20130101; H01Q 1/246 20130101; H01Q
3/2605 20130101 |
Class at
Publication: |
455/562.1 ;
455/073; 455/561 |
International
Class: |
H04B 001/38 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 19, 2003 |
KR |
10-2003-0094126 |
Apr 19, 2004 |
KR |
10-2004-0026722 |
Claims
What is claimed is:
1. A transceiver for a base station with a smart antenna having a
plurality of antennas, comprising: a multipath searching unit for
searching multipath delay information for each demodulation channel
for signals received through the antennas; a demodulating unit for
forming an adaptive beam for each demodulation channel by using the
multipath delay information for each demodulation channel for
receiving signals, performing demodulation to the received signals,
and outputting at least one adaptive beam weight vector for each
demodulation channel, the adaptive beam weight vector being
occurred during demodulation; a controlling unit for selecting at
least one downlink beam index for each channel by using correlation
of the adaptive beam weight vector and the pre-established
plurality of switched beam weight vectors; and a modulating unit
for selecting the downlink switched beams corresponding to at least
one downlink beam index respectively, forming switching beams for
modulating signals of each channel, and outputting the modulated
signals in downlink.
2. The transceiver of claim 1, wherein the demodulating unit
comprises a plurality of demodulators, and each demodulator
comprises: a plurality of adaptive beamforming finger blocks; and a
combiner for combining the outputs from the plurality of adaptive
beamforming finger blocks and outputting the combined outputs to a
channel decoder.
3. The transceiver claim 2, wherein the plurality of adaptive
beamforming finger blocks comprises: an adaptive beam weight vector
operator for real-time extracting the adaptive beam weight vector
from the received signals by using the multipath delay information;
a multiplier for real-time multiplying the received signals by the
outputs from the adaptive beam weight vector operator; and a finger
for receiving the output from the multiplier, performing
dispreading of the DS-CDMA signals by using the multipath delay
information, performing time-tracking, channel estimating, and
coherent demodulation, transferring the demodulated symbol to the
combiner, and continuously outputting a time averaged energy of the
demodulated symbol, and the adaptive beam finger block real-time
provides the adaptive beam weight vector outputted from the
adaptive weight vector operator and the symbol energy from the
finger to the controlling unit.
4. The transceiver of claim 1, wherein the controlling unit
comprises: a weight vector table, in which switched beam weight
vectors are pre-established in accordance with an uplink frequency;
a per-channel adaptive beam weight vector selector for selecting at
least one adaptive weight vector from the plurality of the adaptive
beam weight vectors outputted from the demodulating unit, the
selection beginning from the vector with greatest finger energy; a
per-channel vector inner product and square device for finding the
inner product of the selected adaptive beam weight vector and the
switched beam vector of the weight vector table and outputting its
squared inner product; and a per-channel beam index selector for
selecting a beam index from outputs of the vector inner product and
square device and outputting a downlink beam index.
5. The transceiver of claim 4, wherein the beam index selector
calculates squared inner products vectors such as equation
W.sub.t,k=.parallel.R.sub- .i.sup.HA.sub.k.parallel..sup.2 (here,
the H is an hermitian operator) from at least one adaptive
beamforming weight vector A.sub.k(k=0,1, . . . ,K) selected from
the per-channel adaptive beam weight vector selector; and the
switched beamforming weight vectors R.sub.j(j=0,1, . . . ,L) which
number is same with the number of pre-stored switched beams in
downlink; and selects the downlink beam index by using the squared
inner products vectors.
6. The transceiver of claim 4, wherein an uplink switched beam
weight vector producing the same pattern with the downlink switched
beam pattern, is used, of which frequency is set in uplink, when a
FDD (frequency division duplex) method having different frequencies
between the downlink and the uplink is used.
7. The transceiver of claim 4, wherein the per-channel adaptive
beam weight vector selector selects at least one beam index and
uses the beam index as a downlink switched beam index from squared
inner product of the downlink switched beam, the selection
beginning from the greatest squared inner product, when the number
of the adaptive beam weight vector selected from the per-channel
adaptive beam weight vector selector is 1.
8. The transceiver of claim 4, wherein the switched beam weight
vector table is commonly used for the channels in which the
downlink switched beam is formed.
9. The transceiver of claim 4, wherein the downlink beam index to
any channel is selected based on total receiving energy for each
switched beam for the channel.
10. The transceiver of claim 1, wherein the modulating unit
comprises: a plurality of modulators for modulating the encoded
data for each channel at the base station for downlink transmission
according to the W-CDMA reference and dispersing the modulated
data; a plurality of per-channel downlink beam selectors for
selecting at least one downlink switched beam by using at least one
downlink index for each channel, and outputting the signals
outputted from the modulators as the selected downlink switched
beam; a plurality of per-beam adders for adding each output from
the plurality of the downlink beam selectors for each beam; a
plurality of downlink switched beam formers for forming each
switched beam by using the downlink switched beam weight vector
pre-established at each beam; and a plurality of per-antenna adders
for adding each output from the plurality of downlink switched beam
formers at each antenna and outputting the added output.
11. The transceiver of claim 10, wherein each downlink beam
selector outputs at least one switched beam and does not output
other beams which are not selected.
12. The transceiver for a base station for forming downlink
switched beam in a wireless communication system comprising: a
plurality of array antennas for providing a beam pattern to a
terminal user in downlink or uplink; an RF/IF converter for
converting signals transmitting or receiving through the array
antennas from a radio frequency band to an immediate frequency
band; a multipath searcher for searching a multipath delay
information for signals received from each channel through the
array antenna; an adaptive beamforming demodulator for forming an
adaptive beam for each demodulation channel for receiving signals
by using the multipath delay information for each demodulation
channel and performing demodulation to the received signals, and
outputting the adaptive beam weight vector for each channel, the
adaptive beam weight vector being occurred during demodulation; a
downlink beam controller for selecting at least one downlink beam
index for each channel by using correlation of the adaptive beam
weight vector and the established plurality of switched beam weight
vectors; and a switching beamforming modulator for selecting at
least one downlink switched beam corresponding to at least downlink
beam index respectively, forming switching beams to the modulating
signals for each channel, and outputting the modulated signals
switching beams in downlink.
13. A downlink switched beamforming method at a base station with a
plurality of antennas comprising: a) searching multipath delay
information on signals received through the antennas for each
demodulation channel; b) forming an adaptive beam for receiving
signals for each demodulation channel by using the multipath delay
information, and performing demodulation to the received signals;
c) outputting an adaptive beam weight vector for each channel,
occurred during demodulation; d) selecting at least one downlink
beam index for each channel by using correlation of the adaptive
beam weight vector and the established plurality of switched beam
weight vectors; and e) selecting downlink switched beams
corresponding to at least one downlink beam index respectively,
forming switching beams for modulating signals of each channel, and
outputting the modulated signals in downlink.
14. The downlink switched beamforming method of claim 13, wherein
in the stage d), squared inner products vectors such as equation
W.sub.t,k=.parallel.R.sub.i.sup.HA.sub.k.parallel..sup.2 (here, the
H is an hermitian operator) is calculated from at least one
adaptive beamforming weight vector A.sub.k(k=0,1, . . . ,K)
selected from the per-channel adaptive beam weight vector selector;
and the switched beamforming weight vectors R.sub.j(j=0,1, . . .
,L) of which number is same with the number of pre-stored switched
beams in downlink; and the downlink beam index is selected by using
the squared inner products vectors.
15. The downlink switched beamforming method of claim 13, wherein
in the stage d), the uplink switched beam weight vector is used,
the uplink switched beam weight vector forming the same pattern
with the downlink beam pattern, of which frequency in uplink is set
with the switched beamforming weight vector, when frequency in
downlink is different from the frequency in uplink.
16. The downlink switched beamforming method of claim 13, wherein
in the stage d), at least one beam index is selected from the
squared inner product of the downlink switched beam and used as a
downlink beam index, the selection being made the greatest squared
inner product as reference when the number of the adaptive beam
weight vector is 1.
17. The downlink switched beamforming method of claim 13, wherein
in the stage d), the downlink beam index is selected based on total
receiving energy for each switched beam.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of Korea
Patent Application No. 2003-94126 filed on Dec. 19, 2003 and
Application No. 2004-26722 filed on Apr. 19, 2004 in the Korean
Intellectual Property Office, the entire content of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] (a) Field of the Invention
[0003] The present invention relates to a transceiver for a base
station with a smart antenna and a beamforming method in
downlink.
[0004] More specifically, the present invention relates to a
transceiver for a base station with a smart antenna for
transferring signals from the base station to a mobile station, and
a beamforming method in downlink in a wireless communication system
using an antenna array or the smart antenna.
[0005] (b) Description of the Related Art
[0006] A mobile communication system makes it possible to
communicate any kind of data with certain parties anywhere and at
any time at all. To perfectly embody the mobile communication
system, a next generation mobile communication system is
commercialized which works based on a single reference protocol
standardized all over the world and makes it possible to provide a
far better service.
[0007] The next generation mobile communication system transmits
and receives video and other data in addition to the speech data
being serviced at present. Further, as the services become more
varied, the bandwidth of transceiver data uses far wider band than
the bandwidth at present. Thus, this would make demand for the
mobile communication network increase.
[0008] Thus, the main objective of the next generation mobile
communication system is to provide a method using as narrow a
bandwidth as possible, and reliably transferring more data.
[0009] However, there are no known methods satisfying both
reduction of the bandwidth and increase of reliability at the same
time. Thus, the known methods can not solve both a capacity problem
and a reliability problem arising with the next generation mobile
communication system.
[0010] In recent years, a new method has been actively studied,
which can satisfy both increase of capacity in the communication
system and improvement of reliability. The new method may restrict
interference and noises by controlling beam pattern. The new method
is referred to as `Smart antenna technology`, and is one of the
main technologies for the next generation mobile communication
system.
[0011] In the smart antenna method, a base station sets a best
suited beam to a subscriber of the wireless communication terminal,
and this smart antenna method can reduce radio wave interference,
increase capacity of the communication and improve the quality of
the communication.
[0012] For example, the smart antenna system built at the base
station actively meets the speed of targets including 1) a fixed
target such as offices, 2) a target moving at low speed such as
humans and satellites, and 3) a target moving at fast speed such as
vehicles and trains; and continuously provides the best suited beam
pattern. The smart antenna system provides best gain to the
direction of the target and provides relatively small gain to the
other directions to achieve restriction of interference. That is,
the smart antenna system may increase capacity of the mobile
communication system and improve the communication reliability.
[0013] Therefore, the smart antenna will be applied to the next
generation communication method such as W-CDMA and CDMA 2000 etc.
which are required to transfer many data reliably.
[0014] Meanwhile, when the smart antenna is applied to the base
station for the wireless communication circumstance, the adaptive
beamforming method and switched beamforming method can be
considered as methods applicable in downlink or uplink.
[0015] The adaptive beamforming method forms a beam by continuously
and adaptively changing a beam weight vector in accordance with
circumstances where channels are changed.
[0016] On the other hand, the switched beamforming method has a
predetermined number of beams and predetermines the switched beam
weight vector. The switched beamforming method changes a switched
beam index 120 and forms a beam in accordance with an antenna array
direction of the mobile station as shown in FIG. 1. FIG. 1 shows a
switched beam pattern in downlink according to the traditional
method.
[0017] Generally, the adaptive beamforming method is widely used at
the uplink base station. However, a time division multiplexing
(TDD) method and a frequency division multiplexing (FDD) method are
considered to determine the beamforming method. The adaptive
beamforming method is widely used, using the uplink adaptive beam
weight vector in downlink, when the time division multiplexing
(TDD) method is applied, which frequencies are the same in downlink
and uplink.
[0018] However, since frequencies in downlink and uplink are
different in the frequency division multiplexing (FDD) method, the
adaptive beam weight vector in uplink can not be applied in
downlink. Here, the mobile station measures a channel in downlink
and feedbacks the channel information to the base station. Thus,
the adaptive beamforming or the switched beamforming methods are
used in downlink.
[0019] That is, the traditional method receives the feedback
information from the terminal and performs beamforming in downlink.
In addition, the other method estimates DOA of receiving signals
regardless of a demodulator and uses the DOA for beamforming in
downlink.
[0020] The mentioned method that the mobile station measures the
channel information and feedbacks the channel information to the
base station and applies the channel information to the
beamforming, can be effective, when the characteristics of the
channel are good or the speed of the mobile station is low.
However, errors can occur at the channel during feedback of the
channel information or the performance can fall by feedback delay
etc., when the characteristics of the channel are bad or the speed
of the mobile station is high.
[0021] Further, since the mobile station continuously measures the
characteristics of the channel in downlink and feedbacks the
characteristics of the channel to the base station, the mobile
station may become complicated. Further, since the feedback
information is loaded in uplink, the capacity in uplink is
reduced.
[0022] Meanwhile, as shown in FIG. 2, there is another method
performing the switched beamforming in downlink. FIG. 2 shows a
construction of a transceiver for determining the switched beam
index in downlink using the search result by a switching
beamforming searcher in uplink according to the traditional method.
The detailed operation for each block will be described with
reference to FIG. 3.
[0023] The transceiver of the base station shown in FIG. 2 includes
a switching beamforming multi-channel searcher 260. The switching
beamforming multichannel searcher selects a beam index of which
receiving signal energy is greatest. The beam index is used as a
switched beam index in downlink. In the transceiver of the base
station, since the switching beamforming multi-channel searcher 260
searches all switched beam patterns, the complexity of the
switching beamforming multi-channel searcher 260 increases along
the number of the switched beam. For example, when a search range
with 1/2 chip resolution is 64 chips in the W-CDMA mobile
communication system, 128 correlators are required for the general
searcher. However, 128.times.12 correlators are required for the
switching beamforming multi-channel searcher 260 forming 12
beams.
[0024] Meanwhile, the U.S. Pat. No. 5,634,199 (filed in Apr. 17,
1995) discloses an invention entitled "Method of Subspace
Beamforming using Adaptive Transmitting Antennas with Feedback".
The invention relates to a method for finding channel information
in downlink and a method for finding a beamforming weight in
downlink in the CDMA mobile communication system.
[0025] In detail, according to the U.S. Pat. No. 5,634,199, the
base station transmits several probe signals and the terminal finds
a correlating matrix for the probe signal and feedbacks the
correlating matrix to the base station. Thus, the amount of the
feedback data from the mobile station to the base station can be
reduced. Then, the base station calculates the beamforming weight
in downlink by using the correlating matrixes feedbacked from each
terminal. However, since the invention uses the adaptive
beamforming method using the feedback information from the mobile
station in downlink, the performance can fall, when the
characteristics of the channel are bad.
[0026] Meanwhile, the Korean patent application No. 2000-67975
(filed in Nov. 16, 2000) discloses the invention entitled "Downlink
beamforming system using uplink array response vector and method
thereof". The invention provides a downlink beamforming system for
forming an antenna beam with maximum gain to the direction the user
is located.
[0027] In detail, according to the Koran patent application No.
2000-67975, two methods are proposed for forming a beam in downlink
by using the received array response vector estimated in uplink.
The first method relates to an algorithm that estimates the DOA of
receiving signals and forms the maximum antenna gain to a desired
user's direction, and the method increases the speed for estimating
DOA. The second method estimates the received antenna response
vector by using the received array response vector. The
transmitting beamforming weight vector can be directly found by
multiplying the received antenna response vector by a response
conversion matrix. Thus, the antenna beam with maximum gain to the
direction the user is located, can be formed. However, the
complexity of the base station is not considered in the
invention.
[0028] Meanwhile, the document entitled "Semi-Blind Method for
Transmit Antenna Array in CDMA System" in VTC2000, 1.sup.st volume,
pages 189-194, autumn 2000 discloses a method for finding downlink
channel information by using feedback from the terminal and a
method for finding beamforming weight downlink by using the
downlink channel information, in the CDMA mobile communication
system using the FDD method.
[0029] In detail, the document discloses a method comprising taking
only uplink data, estimating an array response vector from the
uplink data, receiving only the fast fading component as feedback
from the terminal and calculating a downlink beamforming weight
from the fast fading component. Thus, this method can solve the
problem of an open loop beamforming method forming the downlink
beam by using only uplink data. However, although this method can
solve the problem of the pen loop beamforming method to some degree
by using the downlink adaptive beamforming method, the complexity
of the terminal or the base station can be increased.
SUMMARY OF THE INVENTION
[0030] The advantage of the present invention is to provide a
transceiver for a base station with a smart antenna and a
beamforming method in downlink capable of easily forming a downlink
beam by using an inner product of an uplink adaptive beam weight
vector and a switched beam weight vector.
[0031] Another advantage of the present invention is to provide a
transceiver for a base station with a smart antenna and a
beamforming method in downlink capable of improving performance in
downlink without increasing complexity of a terminal or a base
station.
[0032] To achieve the advantage, the present invention provides a
transceiver for a base station with a smart antenna, comprising: a
multipath searching unit for searching multipath delay information
for each demodulation channel for signals received through the
plurality of antennas; a demodulating unit for forming an adaptive
beam for each demodulation channel by using the multipath delay
information for each demodulation channel for receiving signals and
performing demodulation to the received signals and outputting at
least one adaptive beam weight vector for each demodulation
channel, the adaptive beam weight vector occurred during
demodulation; a controlling unit for selecting at least one
downlink beam index for each channel by using correlation of the
adaptive beam weight vector and the pre-established plurality of
switched beam weight vectors; and a modulating unit for selecting
the downlink switched beams corresponding to at least one downlink
beam index respectively and forming switching beam for modulating
signals of each channel and outputting the modulated signals in
downlink.
[0033] Here, the demodulating unit comprises a plurality of
demodulators, and each demodulator may comprise: a plurality of
adaptive beamforming finger blocks; and a combiner for combining
the outputs from the plurality of adaptive beamforming finger
blocks and outputting the combined outputs to a channel
decoder.
[0034] Here, the adaptive beamforming finger blocks may comprise:
an adaptive beam weight vector operator for real-time extracting
the adaptive beam weight vector from the received signals by using
the multipath delay information; a multiplier for real-time
multiplying the received signals by the outputs from adaptive beam
weight vector operator; and a finger for receiving the output from
the multiplier and performing dispreading of the DS-CDMA signals by
using the multipath delay information, and performing
time-tracking, channel estimating, and coherent demodulation, and
transferring the demodulated symbol to the combiner and
continuously outputting a time averaged energy of the demodulated
symbol.
[0035] Here, the adaptive beam finger block real-time provides the
adaptive beam weight vector outputted from the adaptive weight
vector operator and the symbol energy from the finger to the
controlling unit.
[0036] Here, the controlling unit may comprise: a weight vector
table, which switched weight vectors are pre-established in
accordance with uplink frequency; an adaptive beam weight vector
selector for each channel for selecting at least one adaptive
weight vector from the plurality of the adaptive beam weight
vectors outputted from the demodulating unit, the selection
beginning from the vector with greatest finer energy; a vector
inner product and square device for each channel for finding the
inner product of the selected adaptive beam weight vector and the
switched beam vector of the weight vector table and outputting its
squared inner product; and a beam index selector for each channel
for selecting a beam index from outputs of the vector inner product
and square device and outputting a downlink beam index.
[0037] Here, the beam index selector selects the downlink beam
index by using at least one adaptive beamforming weight vector
A.sub.k(k=0,1, . . . ,K) selected from the adaptive beam weight
vector selector for each channel; the switched beamforming weight
vectors R.sub.j(j=0,1, . . . ,L) of which number is same with the
number of pre-stored switched beams in downlink; and an inner
product of vectors such as equation
W.sub.t,k=.parallel.R.sub.i.sup.HA.sub.k.parallel..sup.2 (here, the
H is an hermitian operator).
[0038] Here, an uplink switched beam weight vector producing the
same pattern with the downlink beam pattern is used, of which
frequency is set in uplink, when an FDD method having different
frequencies between the downlink and the uplink is used.
[0039] Here, the adaptive beam weight vector selector for each
channel selects at least one beam index and uses the beam index as
a downlink beam index from squared inner product of the downlink
switched beam, the selection beginning from the greatest squared
inner product, when the number of the adaptive beam weight vector
selected from the adaptive beam weight vector selector for each
channel is 1.
[0040] Here, the switched beam weight vector table is commonly used
for all channels in which the downlink switched beam is formed.
[0041] Here, the downlink beam index to any channel is selected
based on total receiving energy for each switched beam for the
channel.
[0042] Here, the modulating unit may comprise: a plurality of
modulators for modulating the encoded data for each channel at the
base station for transmitting in downlink according to the W-CDMA
reference and dispersing the modulated data; a plurality of
downlink beam selectors for selecting at least one downlink
switched beam by using at least one downlink index for each channel
and outputting the signals outputted from the modulators as the
selected downlink switched beam; a plurality of adders for each
beam for combining each output from the plurality of the downlink
beam selectors for each beam; a plurality of downlink switched beam
formers for forming each switched beam by using the downlink
switched beam weight vector pre-established at each beam; and a
plurality of adders for each antenna for combining each output from
the plurality of downlink switched beam formers at each antenna and
outputs the combination of the output.
[0043] Here, each downlink beam selector outputs at least one
switched beam and does not output other beams which are not
selected.
[0044] Meanwhile, another aspect of the present invention provides
a transceiver for a base station for forming downlink switched beam
in a wireless communication system comprising: a plurality of
antenna arrays for providing a beam pattern to a terminal user in
downlink or uplink; a RF/IF converter for converting signals
transmitting or receiving through the antenna arrays from a
wireless frequency band to an immediate frequency band; a multipath
searcher for searching multipath delay information for signals
received from each channel through the plurality of the antenna
arrays; an adaptive beamforming demodulator for forming an adaptive
beam for each demodulation channel by using the multipath delay
information for each demodulation channel for receiving signals and
performing demodulation to the received signals, and outputting
adaptive beam weight vectors for each channel, the adaptive beam
weight vectors having occurred during demodulation; a downlink beam
controller for selecting at least one downlink beam index for each
channel by using correlation of the adaptive beam weight vector and
the established plurality of switched beam weight vectors; and a
switching beamforming modulator for selecting at least one downlink
switched beam corresponding to at least one downlink beam index
respectively and forming switching beams to the modulating signals
for each channel and outputting the modulated signals switching
beams in downlink.
[0045] Meanwhile, another aspect of the present invention provides
a downlink switched beamforming method at a base station with a
plurality of antennas comprising: a) searching multipath delay
information for each demodulation channel for signals received
through the plurality of antennas; b) forming an adaptive beam for
each demodulation channel by using the multipath delay information
for receiving signals and performing demodulation to the received
signals; c) outputting an adaptive beam weight vector for each
channel, occurred during demodulation; d) selecting at least one
downlink beam index for each channel by using correlation of the
adaptive beam weight vector and the established plurality of
switched beam weight vectors; and e) selecting downlink switched
beams corresponding to at least one downlink beam index
respectively and forming switching beams for modulating signals of
each channel and outputting the modulated signals in downlink.
[0046] Thus, the downlink beamforming method according to the
present invention uses the switched beamforming method but the
downlink beamforming method calculates correlation value of the
adaptive beam weight vector and the plurality of predetermined
switched beam weight vector. The downlink beamforming method
transmits the downlink signal with at least one switched beam of
which correlation values are greatest. The present invention can
improve performance in downlink without increasing complexity of
the terminal or the receiver of the base station.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate an embodiment of
the invention, and, together with the description, serve to explain
the principles of the invention:
[0048] FIG. 1 shows a switched beam pattern in downlink according
to the traditional method.
[0049] FIG. 2 shows a construction of a transceiver for determining
the switched beam index in downlink using the search result by a
switching beamforming searcher in uplink according to the
traditional method.
[0050] FIG. 3 shows a construction of a transceiver for a base
station with multichannel for demodulating signals by forming an
adaptive beam and using an adaptive beam weight vector occurred at
the demodulation to a switched beamforming in downlink, according
to an exemplary embodiment of the present invention.
[0051] FIG. 4 shows an adaptive beamforming multichannel
demodulator block according to an exemplary embodiment of the
present invention.
[0052] FIG. 5 shows a multichannel downlink beam controller block
according to an exemplary embodiment of the present invention.
[0053] FIG. 6 shows a switched beamforming multichannel modulator
block according to an exemplary embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0054] In the following detailed description, only the preferred
embodiment of the invention has been shown and described, simply by
way of illustration of the best mode contemplated by the
inventor(s) of carrying out the invention. As will be realized, the
invention is capable of modification in various obvious respects,
all without departing from the invention. Accordingly, the drawings
and description are to be regarded as illustrative in nature, and
not restrictive. To clarify the present invention, parts which are
not described in the specification are omitted, and parts for which
similar descriptions are provided have the same reference
numerals.
[0055] Hereinafter, a transceiver for a base station with a smart
antenna and a switched beamforming method in downlink are described
with reference to the appended drawings.
[0056] FIG. 3 shows a construction of a transceiver for a base
station with multichannel for demodulating signals by forming an
adaptive beam and using an adaptive beam weight vector occurred at
the demodulation to a switched beamforming in downlink, according
to an exemplary embodiment of the present invention. As shown in
FIG. 3, a multichannel downlink beam controller block 500 is
located between a modulator block 600 and a demodulator block
400.
[0057] As shown in FIG. 3, the transceiver for the base station
with a plurality of antennas according to the present invention
includes a multichannel encoder block 310, a switching beam
multichannel modulator block 600, a radio frequency/intermediated
frequency (RF/IF) converter block 330, N antenna arrays 340, a
multichannel multipath searcher block 360, an adaptive beamforming
multichannel demodulator block 400, a multichannel downlink beam
controller block 500, and a multichannel decoder block 370. The
downlink switched beamforming apparatus for the base station with
polarity antennas according to an exemplary embodiment of the
present invention can comprise the multichannel multipath searcher
block 360, the adaptive beamforming multichannel demodulator block
400, the multichannel downlink beam controller block 500 and the
switching beam multichannel modulator block 600.
[0058] As referred to in FIG. 3, the multichannel multipath
searcher block 360 selects at least one signal among N signals
received through the N antenna arrays 340 and searches multipath
delay information for each demodulation channel. Here, the channel
means a modulator/demodulator pair instead of a wireless channel,
and the M channels are shown in the appended drawing.
[0059] The adaptive beamforming multichannel demodulator block 400
forms an adaptive beam for each demodulation channel by using the
multipath delay information for receiving signals and performs
demodulation to the received signals. The adaptive beamforming
multichannel demodulator block 400 outputs at least one adaptive
beam weight vector for each demodulation channel. At this time, the
adaptive beam weight vector occurs during the demodulation.
[0060] Further, the multichannel downlink beam controller block 500
selects at least one downlink beam index for each channel by using
correlation of the adaptive beam weight vector and the established
plurality of switched beam weight vectors and provides the selected
downlink beam index to the switching beam multichannel modulator
block 600.
[0061] The switching beam multichannel modulator block 600 selects
downlink switched beams corresponding to at least one downlink beam
index and forms switching beams for modulating signals of each
channel and outputs the modulated signals in downlink.
[0062] Meanwhile, FIG. 4 shows a DS-CDMA adaptive beamforming
multichannel demodulator block using an adaptive beamforming method
according to an exemplary embodiment of the present invention. FIG.
4 indicates that adaptive beams are formed from the received
signals for each demodulation channel, and adaptive beam weight
vectors occurred at the demodulation are outputted for each
demodulation channel.
[0063] As shown in FIG. 4, the adaptive beamforming multichannel
demodulator block 400 of the exemplary embodiment of the present
invention includes a plurality of demodulators (400-1.about.400-M).
Each demodulator includes a plurality of adaptive beamforming
finger blocks (420-1.about.420-F) and a combiner 410. The combiner
combines outputs from the adaptive beamforming finger blocks and
outputs the combined output to a channel decoder.
[0064] Here, each adaptive beamforming finger block
(420-1.about.420-F) includes adaptive beam weight vector operators
(421-1.about.421-F) real-time extracting the adaptive beam weight
vector from the received signals by using the multipath delay
information; multipliers (422-1.about.422-F) real-time multiplying
the received signals by the outputs from the adaptive beam weight
vector operator; and fingers (423-1.about.423-F). The fingers
receive the outputs from the multipliers and perform dispreading of
the DS-CDMA signals by using the multipath delay information, and
perform time-tracking, channel estimating, and coherent
demodulation. Also the fingers provide the demodulated symbols to
the combiner and output the time averaged energy of the demodulated
symbol to the controller.
[0065] Here, the adaptive beam finger block real-time provides the
adaptive beam weight vector outputted from the adaptive weight
vector operator and the symbol energy from the finger to the
controller.
[0066] FIG. 5 shows a multichannel downlink beam controller block
according to an exemplary embodiment of the present invention. The
multichannel downlink beam controller block 500 can control a total
M channels (520-1.about.520-M) independently at the same time. The
multichannel downlink beam controller block 500 comprises an uplink
switched beamforming weight vector table 510, an adaptive beam
weight vector selector for each channel 521, a vector inner product
and square device for each channel 522, and a beam index selector
for each channel 523.
[0067] The weight vector table 510 pre-established the weight
vectors corresponding to forming the switched beam in uplink
frequency, and the adaptive beam weight vector selector for each
channel 521 selects at least one of the adaptive weight vectors
from the plurality of the adaptive beam weight vectors
corresponding to the channel outputted from the demodulator block
400. The selection begins from the greatest adaptive beam weight
vector.
[0068] Further, the vector inner product and square device for each
channel 522 finds the inner product of the selected adaptive beam
weight vector and the switched beam vector of the weight vector
table and outputs its squared inner product. The beam index
selector 523 selects at least one beam index from the inner product
of vectors and the output from the square device and outputs the
downlink beam index.
[0069] Meanwhile, FIG. 6 shows a switching beamforming multichannel
(M channels) modulator block according to an exemplary embodiment
of the present invention. The switching beam multichannel modulator
block 600 comprises a plurality of modulators (610-1.about.610-M),
downlink beam selectors for each channel (620-1.about.620-M), a
plurality of adders for each beam (the number is L)
(630-1.about.630-L), a plurality of downlink switched beam formers
(640-1.about.640-L), and adders for each antenna
(650-1.about.650-N). The plurality of modulators
(610-1.about.610-M) modulate the encoded data at each channel of
the base station and disperse those according to the W-CDMA
reference. The downlink beam selectors for each channel
(620-1.about.620-M) select at least one downlink switched beam by
using the downlink index and output the signals outputted from the
modulators as the selected downlink switched beam. The L adders for
each beam (630-1.about.630-L) combine each output from the
plurality of the downlink beam selectors. The plurality of downlink
switched beam formers (640-1.about.640-L) form each switched beam
by using the downlink switched beam weight vector pre-established
for each beam. The adders for each antenna (650-1.about.650-N)
combine each output from the plurality of downlink switched beam
formers and output the result.
[0070] Here, the switched beamforming method in downlink according
to the exemplary embodiment of the present invention is described
with reference to FIGS. 3.about.6.
[0071] First, as shown in FIG. 3, the downlink beam controller
block 500 periodically receives at least one uplink adaptive beam
weight vector A.sub.j(j=1,2, . . . ,P) for each channel of
communication, from the adaptive beamforming demodulator block 400.
The P is same or greater than 1, and the P may be same with the
number of the fingers if the exemplary embodiment is applied to the
DS-CDMA method. Further, the estimated energies for each finger are
provided if the exemplary embodiment is applied to the DS-CDMA
method.
[0072] Traditionally, a base station for the DS-CDMA mobile
communication system includes a plurality of demodulators capable
in order to receive signals from a plurality of terminals which the
base station provided. Each demodulator includes a plurality of
fingers to get diversity gain along multipath of the channel.
[0073] At this time, the receiver combines the outputs of the
plurality of fingers and achieves diversity gain so that fading
effect according to network condition is reduced. For example, the
antenna of the base station receives several signals having
different transfer delay through multipath. The signals were the
same RF signals transmitted from the terminal. The controller of
the receiver assigns the different multipath to each finer, and
combines the results demodulated at each finger. Thus the
controller can achieve the path diversity to improve the
performance of the recover.
[0074] Further, the receiver of the base station for the CDMA
mobile communication system includes an energy estimator for each
finger for estimating energy. The common energy estimator
calculates the signal energy which the finger took and averages
plurality of signal energies and estimates the finger energy based
on the average signal energy by using a table for mapping the
energy to estimated values.
[0075] The adaptive beam weight vectors A.sub.j(j=0,1, . . . ,P)
are the normalized weight vectors which are real-time used for
forming the adaptive beams for each finger, when the demodulators
demodulate the received signals.
[0076] First, as shown in FIG. 4, the demodulator block 400 outputs
the adaptive beam weight vector for each finger and the finger
energy to the downlink beam controller block 500. The adaptive beam
weight vector for each finger and the finger energy is used for
demodulating for each channel.
[0077] Next, as shown in FIG. 5, the downlink beam controller block
500 receives at least one adaptive weight vector and finger energy
for each communication channel from the demodulator block 400. The
adaptive beam weight vector selector 521 shown in FIG. 5 selects at
least one adaptive weight vector A.sub.k(k=0,1, . . . ,K)
(K.ltoreq.P . . . The selection begins from the vector with
greatest finer energy.
[0078] The vector inner product and square device for each channel
522 finds each inner product of the selected K adaptive beam weight
vectors A.sub.k(k=0,1, . . . ,K) and the normalized uplink switched
beam vectors R.sub.j(j=0,1, . . . ,L) of the uplink switched beam
weight vector table 510 and outputs its squared inner products. The
beam index selector 523 selects at least one downlink beam index by
using the L.times.K inner products squared of vectors and transfers
the selected downlink beam index to the modulator block 600
corresponding to the channels 520-1.about.520-M.
[0079] Meanwhile, the following equation 1 shows the inner product
squared of the i(i=1,2, . . . ,L) th uplink switched beam weight
vector and the k(k=1,2, . . . ,K) th uplink adaptive beam weight
vector. H indicates an hermitian operator.
W.sub.t,k=.parallel.R.sub.i.sup.HA.sub.k.parallel..sup.2 [Equation
1]
[0080] Further, when the number of the adaptive beam weight vector
K is 1, at least one beam index can be selected from the inner
products squared of vectors. The selection begins from the greatest
one. The beam index can be used as the downlink switched beam
index.
[0081] Further, the switched beam weight vectors corresponding to
the number of the downlink switched beam are commonly used for all
modulation channels forming the downlink switched beam.
[0082] Here, although the switched beam pattern is used in the
downlink, the beam weight vector can be different in accordance
with the frequencies, when the frequencies of the downlink and
uplink are different, for example in the FDD method. Thus, the L
uplink switched beam weight vectors are defined.
[0083] That is, when the exemplary embodiment of the present
invention performing the switching beamforming in downlink by using
the switched beam pattern as shown in FIG. 1 is used as a FDD
method, it is more effective to use the uplink switched beam weight
vector meeting the uplink frequency producing the same pattern with
the downlink beam pattern, than to take direct inner product of the
uplink adaptive beam weight vector and the downlink switched weight
vector.
[0084] In the equation 1, several methods can be suggested for
selecting the downlink switched beam index by using the L.times.K
inner products squared of vectors W.sub.t,k. Here one of the
methods is described.
[0085] First, a total energy for each switched beam can be defined
by the following equation 2. 1 W i = k = 1 K e k W i , k [ Equation
2 ]
[0086] Here, the e.sub.k is a demodulation energy of a kth finger,
the W.sub.t,k means the inner product squared of the uplink
switched beam weight vector and the uplink adaptive weight vector
as defined in equation 1. Equation 2 means a total energy of K
fingers in direction to the ith switched beam.
[0087] The beam index selector according to the exemplary
embodiment of the present invention calculates W.sub.t(i=1,2, . . .
,L) from equation 2, and selects at least one beam index from the
greatest one. The beam index selector transfers the selected beam
index to the modulator corresponding to the channel.
[0088] As referred to in FIG. 6, the switching beamforming
multichannel modulator block 600 receives at least one beam index
selected for each channel from the downlink beam controller block
500, and selects at least one downlink switched beam for each
channel from the downlink beam selectors (620-1.about.620-M) in the
multichannel modulator block 600 by using the switched index.
[0089] Further, the number of output ports of each downlink beam
selector (620-1.about.620-M) is L, and the number of the output
ports is same with the number of the downlink beams. The downlink
beam selector sends at least one switched beam selected from the L
switched beams but does not send others. That is, the output for
the other beams not selected is 0.
[0090] The L output ports of each downlink beam selector
(620-1.about.620-M) are connected to input ports of each
corresponding adders for each beam (630-1.about.630-L). The adders
for each beam (630-1.about.630-L) receive the total M inputs from
each downlink beam selector and combines the M inputs at each
beam.
[0091] Each downlink switched beamforming unit (640-1.about.640-L)
receives outputs from the L adders for each beam
(630-1.about.630-L) and multiplies the outputs from the adders by
the downlink switched beam weight vectors predetermined for each
beam.
[0092] When the downlink switched beamforming unit
(640-1.about.640-L) performs downlink beamforming, the N (that is,
the number of antennas) switched beam-weight vectors for each beam
are multiplied by the input signals. Thus the number of the outputs
becomes N.
[0093] The N outputs for each L downlink switched beamforming unit
(640-1.about.640-L) are combined at the adders for each antenna
(650-1.about.650-N). The combined output is transferred to the
RF/IF converter 330 shown in FIG. 3.
[0094] Meanwhile, the multichannel downlink beam controller block
500 can be located in the switching beamforming multichannel
modulator block 600 or the adaptive beamforming multichannel
demodulator block 400.
[0095] In conclusion, the downlink beamforming method according to
the exemplary embodiment of the present invention uses the switched
beamforming method but the downlink beamforming method calculates
correlation value of the adaptive beam weight vector and the
plurality of predetermined switched beam weight vectors. The
adaptive beam weight vector occurs when the signals received from
the mobile station are demodulated according to the adaptive
beamforming method. The downlink beamforming method transmits the
downlink signal with at least one switched beam of which
correlation value is greatest.
[0096] The traditional methods received the feedback information
from the terminal for forming the downlink beam or estimated DOA of
receiving signals for forming the downlink beam. However, the
exemplary embodiment of the present invention can form the downlink
beam without increasing complexity of the terminal or the receiver
at the base station.
[0097] While this invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not
limited to the disclosed embodiments, but, on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
[0098] The present invention can easily form the downlink beam in
the wireless system using the antenna array or the smart antenna by
using the inner product of the uplink adaptive beam weight vector
and the switched beam weight vector.
[0099] Further, the present invention can improve the performance
of the downlink without increasing complexity of the terminal or
the receiver at the base station.
* * * * *